JPS60191447A - Optical disk - Google Patents

Abstract

PURPOSE:To obtain an optical disk which decreases warpage and twist in highly moiste environment and has excellent double refractivity and transparency by using a base material consisting of a polymer formed by polymerizing the fluoroalkyl (meth)acrylate expressed by the specific constitutional formula as an essential raw material. CONSTITUTION:A polymer obtd. by polymerizing the fluoroalkyl (meth)acrylate expressed by the formula I as an essential material is formed as a base material. Z is preferably incorporated in the form of CH2 in the fluoroalkyl (meth)acrylate to be used as the essential raw material. More specifically, the fluoroalkyl methacrylate is more preferable to the fluoroalkyl acrylate and the polymer having the higher glass transition temp. Tg and better heat resistance is obtainable with the Z incorporated in the form of CH3. The better result is obtd. as y is smaller in a 0-4 range in order to satisfy both of the glass transition point and water absorptivity. Rf may be n-alkyl, alicyclic alkyl, etc. and more preferably a branched alkyl. The better result is obtd. as the C is larger within a 1-20 range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical information recording disc that reads recorded signals by reflection or transmission of laser light.

[Background technology]

Optical discs currently in common use contain methyl methacrylate as a main component, and are therefore susceptible to warping and twisting, especially when placed in humid environments. The occurrence of warpage and twisting becomes a major hindrance to accurate reproduction of recorded information. Therefore, in order to improve water absorption and reduce the occurrence of warping and twisting, styrene is copolymerized with methyl methacrylate. However, when a large amount of styrene is copolymerized, a new problem arises in that birefringence increases.

[Purpose of the invention]

This invention was made in view of these circumstances,
It is less likely to warp or twist even in a humid environment, and
The objective is to provide an optical disc with excellent birefringence and transparency.

[Disclosure of the invention]

In order to achieve the above objectives, the inventors first
We focused on using a polymer made by polymerizing fluoro(meth)acrylate as an essential raw material as a base material. The reason why fluoro(meth)acrylate was selected as an essential raw material is
Poly(meta) has high light transmittance and low birefringence.
This is because by taking advantage of the advantages of acrylic ester, its disadvantages of poor water absorption and heat resistance can be improved by improving water repellency through fluorine substitution and strengthening intermolecular bonding strength. . In general, poly(meta)
When acrylic acid ester is substituted with fluorine, its glass transition temperature increases by several tens of degrees, improving its heat resistance and significantly reducing its water absorption. As a result of further research, the inventors discovered a type of fluoro(meth)acrylate suitable for use in optical discs, and have now completed this invention.

Therefore, the gist of the present invention is an optical disk whose base material is a polymer obtained by polymerizing fluoroalkyl (meth)acrylate represented by the following structural formula as an essential raw material.

1 RtCCH2')y-0-C-C=CH2Z; CH
3 or H y; 0-4 Rf; fluoroalkyl group having 1 to 20 carbon atoms This expression 13j4 will be explained in detail below.

Here, in the fluoroalkyl (meth)acrylate of the above formula used as an essential raw material, Z is preferably CH3. That is, fluoroalkyl methacrylate is more preferred than fluoroalkyl acrylate. The glass transition temperature (
This is because a polymer having a high Tg) and excellent heat resistance can be obtained. Incidentally, the Callus transition point increases as the number of branches (including a ring) of the alcohol component Rt (CH2)y- of the ester increases and as the number of carbon atoms decreases. On the other hand, the water absorption rate decreases when y is decreased and the total number of carbon atoms in R is increased to increase the fluorine content in the polymer. Therefore, in order to satisfy both the glass transition point and the water absorption rate, y is preferably smaller in the range of 0 to 4, and may be RtIdn-alkyl, alicyclic alkyl, etc., but branched alkyl is preferable. is preferred, and the number of carbon atoms is preferably as large as 1 to 20.

Furthermore, it is preferable that the group is completely substituted to become a perfluoroalkyl group. When viewed as Rr(Cfh)y-, it is preferable that the number of carbon atoms is :) to 8 and branched. For example, preferred examples include those represented by the following formula.

Polyfluoroalkyl (meth)acrylate (homopolymer) obtained by polymerizing fluoroalkyl (meth)acrylate alone may be used as a base material, but one or more other types may be used as long as the purpose of the present invention is not impaired. A copolymer with a monomer may be used as the base material. In this case, it is preferable that the proportion of fluoroalkyl (meth)acrylate used be as high as possible. Other monomers include, for example,
(Meth)acrylic acid esters and other vinyl monomers are preferably used. As the (meth)acrylic ester, it is preferable to use a branched (meth)acrylic ester. Other vinyl monomers, vinyltoluene, ethylstyrene, isopropylstyrene, i-
Phylsterene, p-nonalsunarene, etc. are used, but it is preferable to use p-methylstyrene, which has a thermal decomposition temperature.

When copolymerizing fluoroalkyl (meth)acrylate, (meth)acrylic acid ester, and, if necessary, a vinyl-based product other than both, 80 to 20 M parts of fluoroalkyl (ivy) acrylate, (meth)acrylic It is preferable to copolymerize 10 to 50 parts by weight of the vinyl monomers other than Acid Nether and 9 to 40 parts by weight in a total of 100 parts by weight.

The polymer may be produced by any of the known polymer production methods, such as bulk polymerization, suspension wheel method, solution polymerization method, and emulsion polymerization method.

The components of the base material include auxiliary agents such as silicone, wax, fatty acids, fatty acid esters, fatty acid metal salts, and aliphatic alcohols for the purpose of improving mold releasability from the stamper, and high-grade additives for the purpose of preventing static electricity. Auxiliary agents such as alcohol nurfonic acid salts and +-class ammonium salts may be used in combination with the above-mentioned polymers to the extent that they do not impair the achievement of the objects of the present invention.

The optical Dinuk of the present invention is manufactured, for example, in the following manner. First, a method such as injection molding or direct pressure molding of a polymer is used to transfer pits, which will become recording signals, using a mold set with nutanvar to form a disk base material. Molding must be performed under conditions that minimize residual stress. Next, in the case of a duplicate disc, a reflective layer is generally formed on the bit transfer surface by vacuum deposition of gold maple, sputtering, or ion blasting, and if necessary, a protective coating for the reflective layer is applied. You can go and manufacture it. In addition, in the case of Memory Dinuk, after transferring the bit that becomes the tracking signal in the same manner as above, it is possible for the user to write on the bit surface with, for example, amorphous rare metals or compounds that can be thermally decomposed by laser. An optical disk for memory can be manufactured by fully depositing or coating a recording layer, and further forming a reflective layer or a protective coating as described above, if necessary.

Since the optical disc of the present invention obtained as described above uses a polymer containing fluoroalkyl (meth)acrylate as an essential raw material as a base material, polymethyl methacrylate (PΔ Compared to those using polymers such as (MA) as the base material, the water absorption rate is lower. Usually 0.20
It will be about 4 or less.

Therefore, there is very little chance of warping or twisting due to high humidity. Furthermore, it is optically homogeneous, has excellent birefringence, and has excellent transparency. Furthermore, since the polymer used in this invention usually has a glass transition temperature of about 70°C or higher,
Warping due to heat also causes deformation such as twisting.

Next, examples will be described.

(Example 1) All of the following raw materials were charged into IE's Sebara Purfuranuco. However, parts are by weight.

10) (Fluoroalkyl tacrylate) 1 i Distilled water (contains 0.5 weight percent of hydroxyethyl cellulose) 3 parts Benzoyl peroxide 0.015 parts n-lauryl mercaptan 0.005 i Stirring speed 20
The polymerization reaction was carried out at 0 rpm and a bath temperature of 80° C. for 3 to 4 hours.

After the polymerization was completed, the polymer was sieved through a 70-mesh stainless steel sieve and washed with hot water. Next, the polymer was transferred into a vacuum dryer and dried at 80° C. and 1 mmHg for 24 hours to obtain polymer beads.

A disk base material was molded using the polymer beads.

Next, a reflective layer was formed on the disc base material, and a protective coating of Reflection 1- was applied to create an optical disc.

(Examples 2 and 3) Polymer beads were made in the same manner as in Example 1, except that fluoroalkyl ivy acrylate was used as expressed by the following formula (10). Created an optical disc.

(Example 4) A polymerization reaction was carried out under the same reaction conditions as in Example 1 using fluoroalkyl methacrylate, tutaacrylic acid ester, 40 parts of MMA (methyl methacrylate), and 20 parts of p-menalsunarene as a vinyl monomer. They made beads and then optical discs.

(Example 5) H3O 1II CHz=C-C-0-CHz-(CFz)3-CF3I
15 parts MMA (methyl methacrylate) 35 parts p-
Methylsunarene 15 parts Using the above-mentioned raw materials, a polymerization reaction was carried out under the same reaction conditions as in Example 1 to produce polymer beads, and further, optical Dinuk was produced.

The glass transition temperature and water absorption rate of the polymers obtained in Examples 1 to 5 were measured, and the presence or absence of birefringence of the disk base material was investigated. I looked into it. However, the glass transition temperature was determined by temperature dispersion measurement using a viscoelastic nupectronator, and the temperature at which the dynamic loss (frequency: 10 H) reached its peak was taken. Water absorption rate is JIS K691i
According to the above, the values were taken after immersion in distilled water at 2°C for 24 hours. The presence or absence of birefringence is determined by measuring the presence or absence of birefringence using the Tokyo Kogaku Kikai Co., Ltd.
The determination was made by observing the degree of coloring (interference stripes) using a train viewer. To determine whether or not warping or twisting occurs, check whether or not warping or twisting occurs after leaving an optical 7 disc (with a reflective layer and protective coating) in an environment of 45°C and relative humidity of 95%. Judgment was made by The results are shown in Table 1.

Table 1 From Table 1, the optical discs of Examples 1 to 5 have high glass transition temperatures of the polymers used, so they are less prone to deformation such as warping or twisting due to heat, and have low water absorption, so they can be used in high humidity. It can be seen that no torsion occurs when the material is warped in the environment, and no birefringence occurs.

〔Effect of the invention〕

Since the optical disc according to the present invention is made of a polymer obtained by polymerizing fluoroalkyl (meth)acrylate having the structure represented by the above general formula as an essential raw material, it will not warp or twist even in a humid environment. Moreover, it has excellent birefringence and transparency.

Agent Patent Attorney Takehiko Rei Matsumoto [Ito Roku Neho Seisho (Spontaneous) June 4, 1981 2 Name of the invention Optical Disk 3 Relationship with the person making the amendment Case Patent applicant Location Osaka Prefecture 1048 Kadoma, Kadoma City Name (5)
83) Matsushita Electric Works Co., Ltd. Representative Representative: Iku Kobayashi 4, Agent 6, Specification subject to amendment 7, Contents of amendment (1) The entire text of the scope of claims of the specification will be corrected as shown in the attached sheet. .

(2) [Claims after amendment] 2. Scope of claims (1) Fluoroalkyl (
An optical disc whose base material is a polymer made by polymerizing meth)acrylate as an essential raw material.

Z; CH3 or H y; 0-4 Rf, fluoroalkyl group with 1-20 carbon atoms (2) The polymer contains 80-20 parts by weight of fluoroalkyl (meth)acrylate, (meth)acrylic acid ester 1
Claim 1 which is a copolymer formed by copolymerizing 100 parts by weight of vinyl monomers other than both in a proportion of 0 to 50 parts by weight, respectively. Optical disc as described.

[3] The optical disk (4) polymer according to claim 2, wherein the methacrylic acid ester is methyl methacrylate and the vinyl monomer is alkyl-substituted styrene,
The optical disc according to any one of claims 1 to 3, having a glass transition temperature of 70° C. or more and a water absorption rate of 0.20% or less.

91

Claims (3)

[Claims] (1) An optical disc whose base material is a polymer obtained by polymerizing fluoroalkyl (meth)acrylate having the following structural formula as an essential raw material. Z; CH3 or H y; 0-4 Rf; fluoroalkyl group with 1-20 carbon atoms (2) The polymer is fluoroalkyl (meth)ac IJL
/-t 80-20 parts by weight, (meth)acrylic acid ester 10-50 parts by weight 9 Vinyl monomers other than both 0-40
2. The optical disc according to claim 1, which is a copolymer formed by copolymerizing a total of 1007 ijd parts of each monomer in a proportion of parts by weight. (3) Methacrylic acid ester is methyl methacrylate,
2. The optical disk (4) polymer according to claim 2, wherein the hynyl monomer is an alkyl-substituted styrene, has a glass transition temperature of 70° C. or more. The optical disc according to any one of claims 1 to 3, which has a water absorption rate of 0.20'% or more.